package com.xpert.utils;

import java.util.*;

public class NaturalOrderComparator implements Comparator {

    public static int compareRight(String a, String b) {
        int bias = 0;
        int ia = 0;
        int ib = 0;
        // Thber it in BIAS.e longest run of digits wins. That aside, the greatest
        // value wins, but we can't know that it will until we've scanned
        // both numbers to know that they have the same magnitude, so we
        // remem
        for (;; ia++, ib++) {
            char ca = charAt(a, ia);
            char cb = charAt(b, ib);
            if (!Character.isDigit(ca) && !Character.isDigit(cb)) {
                return bias;
            } else if (!Character.isDigit(ca)) {
                return -1;
            } else if (!Character.isDigit(cb)) {
                return +1;
            } else if (ca < cb) {
                if (bias == 0) {
                    bias = -1;
                }
            } else if (ca > cb) {
                if (bias == 0) {
                    bias = +1;
                }
            } else if (ca == 0 && cb == 0) {
                return bias;
            }
        }
    }

    @Override
    public int compare(Object o1, Object o2) {
        return NaturalOrderComparator.compareTo(o1, o2);
    }

    public static int compareTo(Object o1, Object o2) {
        String a = o1.toString();
        String b = o2.toString();
        int ia = 0, ib = 0;
        int nza = 0, nzb = 0;
        char ca, cb;
        int result;
        while (true) {
            // only count the number of zeroes leading the last number compared
            nza = nzb = 0;
            ca = charAt(a, ia);
            cb = charAt(b, ib);
            // skip over leading spaces or zeros
            while (Character.isSpaceChar(ca) || ca == '0') {
                if (ca == '0') {
                    nza++;
                } else {
                    // only count consecutive zeroes
                    nza = 0;
                }
                ca = charAt(a, ++ia);
            }
            while (Character.isSpaceChar(cb) || cb == '0') {
                if (cb == '0') {
                    nzb++;
                } else {
                    // only count consecutive zeroes
                    nzb = 0;
                }
                cb = charAt(b, ++ib);
            }
            // process run of digits
            if (Character.isDigit(ca) && Character.isDigit(cb)) {
                if ((result = compareRight(a.substring(ia), b.substring(ib))) != 0) {
                    return result;
                }
            }
            if (ca == 0 && cb == 0) {
                // The strings compare the same. Perhaps the caller
                // will want to call strcmp to break the tie.
                return nza - nzb;
            }
            if (ca < cb) {
                return -1;
            } else if (ca > cb) {
                return +1;
            }
            ++ia;
            ++ib;
        }
    }

    static char charAt(String s, int i) {
        if (i >= s.length()) {
            return 0;
        } else {
            return s.charAt(i);
        }
    }

    public static void main(String[] args) {
//        String[] strings = new String[]{"1-2", "1-02", "1-20", "10-20", "fred", "jane", "pic01",
//            "pic2", "pic02", "pic02a", "pic3", "pic4", "pic 4 else", "pic 5", "pic05", "pic 5",
//            "pic 5 something", "pic 6", "pic 7", "pic100", "pic100a", "pic120", "pic121",
//            "pic02000", "tom", "x2-g8", "x2-y7", "x2-y08", "x8-y8"};
        String[] strings = new String[]{"1.1.1", "1.1.10", "1.1.2", "1.1.2.1", "1.1.2.2", "1.1.2.10", "1.1.2.2jj"};
        List orig = Arrays.asList(strings);
        System.out.println("Original: " + orig);
        List scrambled = Arrays.asList(strings);
        Collections.shuffle(scrambled);
        System.out.println("Scrambled: " + scrambled);
        Collections.sort(scrambled, new NaturalOrderComparator());
        System.out.println("Sorted: " + scrambled);
    }
}
